Conventional butterfly valves, such as those used in aircraft fuel systems, control fluid flow rates within a flow channel by adjusting the position of a valve plate, or throttle plate, within the flow channel. For example, rotation of the valve plate from an open position, where a face of the valve plate orients parallel to a flow within the flow channel, to a closed position, where a face of the valve plate orients perpendicular to the flow within the flow channel, decreases the fluid flow rate within the channel.
Typically, when the butterfly valve orients the valve plate in the closed position, an outer periphery of the valve plate contacts a valve seat, such as an O-ring, within the flow channel. Such contact between the valve plate and the valve seat creates a seal that prevents fluid flow through the flow channel. However, over time, as the butterfly valve rotates the valve plate from the closed position to the open position and from the open position to the closed position, the valve plate wears against the valve seat, thereby minimizing the ability for the seal to prevent leakage through the flow channel.
To limit wear between the valve plate and the valve seat, as found in conventional butterfly valves, certain butterfly valve designs provide both rotation of the valve plate to a closed position (e.g. perpendicular to the flow within the flow channel and parallel to the valve seat) and axial translation of the valve plate against the valve seat to seal the valve plate against the seat. For example, butterfly valves configured to provide both rotational and linear positioning of the valve plate, relative to the valve seat, conventionally utilize cam assemblies. Typical cam assemblies include a cam, coupled to a shaft, and mounted within a cam chamber that attaches to a valve plate. When positioning the valve plate from an open to a closed position, for example, as the shaft rotates, the cam engages a first cam chamber surface of the cam chamber and causes the valve plate to rotate within a flow channel to a closed position (e.g., the valve plate face orients perpendicular to a fluid flow direction in the flow channel). As the shaft continues to rotate, the cam rotates within the cam chamber against a second cam chamber surface. Such rotation of the cam linearly positions the valve plate relative to a valve seat and forces the valve plate against the valve seat into a seated position, thereby sealing the flow channel.